How should soil cores be taken in zone sampling?

• A. In a straight line along field boundaries.
• B. Sampling only at the field center.
• C. Randomly in a zigzag pattern, with multiple cores to ensure consistency.
• D. Only one core per grid cell.

Answer: (C)

In zone sampling, you want samples that truly reflect conditions across the whole zone, not just a single spot. Taking soil cores in a random zigzag pattern helps spread the sampling across the area so you don’t bias results by hitting only one part of the field or following a feature like a boundary or a fixed line. Collecting multiple cores within the zone and combining them into a composite sample reduces the influence of small, localized differences and gives a more reliable read on the zone’s fertility, pH, and other properties. It’s also important to sample at a consistent depth so results are comparable across zones.

Choosing a straight line along field boundaries tends to over- or under-represent conditions near those edges. Sampling only at the field center misses variability that exists across the zone, and taking only one core per grid cell fails to capture within-zone variation. The random, multi-core approach balances coverage and replication to produce meaningful, actionable soil test results.